Dry,instant access electrosensitive recording elements and methods

ABSTRACT

VISIBLE IMAGES CAN BE PRODUCED DIRECTLY IN ELEMENTS CONTAINING A LAYER OF CRYSTALLINE POLYACETYLENIC MATERIAL BY APPLYING AN ELECTRICAL POTENTIAL BETWEEN AN ELECTRODE CLOSELY SPACED TO SAID LAYER AND A CONDUCTING BACKING MEMBER ON THE OPPOSITE SIDE OF THE LAYER.

April 10, 1973 BORSENBERGER ETAL 3,726,769

- 'DRY, INSTANT ACCESS ELECTROSENSITIVE RECORDING ELEMENTS AND METHODS Filed D80. 20, 1971 .SE/VS/T/I/E LAYER FIG con/auarwamrm su am ELECTRODE F/@ 2 7; SENSITIVE LAYER con/aucr/vs PAPER L TCO/VOUCT/l/E PLATE United States Patent US. Cl. 204-2 5 Claims ABSTRACT OF THE DISCLOSURE Visible images can be produced directly in elements contaim'ng a layer of crystalline polyacetylenic material by applying an electrical potential between an electrode closely spaced to said layer and a conducting backing member on the opposite side of the layer.

BACKGROUND OF INVENTION Field of invention This invention relates to the field of non-silver instant access imaging and, in particular, to high-speed electrical pulse recording elements and their use in rapid data recording without the need for conventional photographic exposure or processing.

Description of prior art Various means and elements are known for recording electrical signals. For example, it is known to impregnate paper with electrically conductive solutions of electrolytes. These solutions are typically adapted to decompose when a signal impulse is applied. Also, procedures are known wherein a hole is burned in a paper recording blank. Such recordings are only suitable for relatively coarse work where no fine gradations of tonal value are necessary such as in recording telegraphic information or recording process instrumentation curves.

One widely used electrosensitive paper comprises a carbon-impregnated conductive paper bearing a layer of metallic paint on one surface and a powdery light gray coating. During the recording process, the gray coating is at least partially removed by the passage of current from a recording stylus through the paper. These sheets are difficult to handle as they are readily smeared.

Another form of recording element useful in recording electrical signals is described in Dalton US. Pat. No. 3,255,039, issued June 7, 1966. Such elements involve a conductive substrate with an aerated coating which is removable in areas to which an electrical :voltage is applied. This coating includes a film-forming binder, a masking pigment and a multiplicity of microscopic gas bubbles. These elements are rlifficult to prepare in that drying time and temperature must be carefully regulated to prevent the gas bubbles from permanently fracturing the finished coating.

Other types of recording elements require further processing or some post-treatment. Still other elements are temperature sensitive and do not store well.

Thus, there is a need for dry, instant access electrosensitive recording elements which are stable, smudge resislaant, require no post-treatment and are relatively simple to prepare.

SUMMARY OF THE INVENTION We have found that an element comprising a layer of a polyacetylenic compound can be used to produce instant access visible images of the path traced out by an electrode which passes adjacent the surface of the element while an electrical potential is applied between the electrode and a conducting layer on the opposite side of the layer of polyacetylenic compound. When such an electrical potential is applied, the sensitive polyacetylenic compound undergoes direct imagewise polymerization to a highly colored polymeric product. The term imagewise, as used herein, has reference to the applied electrical potential and is not meant to imply visible light images. Thus, imagewise polymerization refers to polymerization occurring in the areas of an applied electrical potential.

This system produces a stable image directly without the need of further processing or post-treatment of any kind. In addition, the present system utilizes non-silver elements which are smudge resistant in a completely dry process.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic representation of one embodiment of an element and the associated electrical connection in accordance with this invention.

FIG. 2 is a schematic representation of another embodiment of an element together with the electrical connection arrangement used therewith.

DESCRIPTION OF PREFERRED EMBODIMENT The objects of the present invention are accomplished by the use of a layer of crystalline polyacetylenic compounds on a conductive support. Layers of various useful polyacetylenic compounds or polyynes are subjected to a concentrated electrical potential as obtained between an electrode closely spaced to the sensitive polyyne layer and a conductive backing member on the opposite side. The terms electrode and conductive backing member are inclusive of any electrical means of accomplishing selective ionization of the atmosphere adjacent a free surface of the polyyne layer. A suitable electrode means for such selective ionization can include a pin electrode, an array of pin electrodes, an addressable conductive grid and the like. When such an electrical potential is applied across the layer, it results in the imagewise polymerization (in the areas of applied potential) of the polyyne material to a highly colored product.

The elements utilized in this invention can take various forms. FIG. 1 is a representation of an element in the form of an insulating support bearing a conducting layer which, in turn, bears a layer of polyyne material. An electrical connection is made to the conductive layer of this element as shown in FIG. 1. An electrical potential is then applied across the sensitive layer between the electrode and the conducting layer. FIG. 2 shows an element wherein the polyyne layer is on a conductive paper which has sufficient conductivity that the electrical connection can be achieved simply by pressing the paper firmly against a metal support or other conductive plate.

The electrosensitive polyacetylenic materials useful in this invention include numerous polyacetylenic compositions reported in the literature as exhibiting color change upon exposure to actinic radiation. Such photosensitive polyacetylenic or polyyne compounds taught in the art contain a minimum of two acetylenic linkages as a conjugated system (i.e., -CEC-CEC) and, with only a few exceptions, carbon atoms in alpha positions to the acetylenic carbon atoms, i.e., those carbon atoms directly connecting to the acetylenic carbon atoms, are bonded directly onto carbon and/ or hydrogen atoms. These photosensitive polyacetylenic compositions of matter encompass diynes, triynes, tetraynes, higher polyynes and numerous derivatives and related compounds thereof of various chemical classes ranging from hydrocarbon compounds to acids, esters, diols, to still other compounds of other chemical classifications containing numerous and varied organic radicals stemming from the conjugated acetylenic carbon atoms, all of which are termed polyyne compounds for purposes of this invention. For purposes of this invention, various polyynes can be used which typically have such low photosensitivity as to have no real utility in the different photographic imaging processes. This advantage arises out of the fact that the present process relies only on the electrosensitivity of the polyyne and not on the photosensitivity.

The term electrosensitivity as used herein has reference to the propensity of various polyyne materals to polymerize to a highly colored polymerization product upon the application of a concentrated electrical potential as described above. It is within the skill of the art to evaluate the electrosensitivity of a polyyne material if this property is unknown. One needs merely to expose samples of prepared crystalline polyacetylenic compositions of matter to an electrical potential as described herein and to observe whether a visible color change occurs in the areas of applied potential. If a visible color change occurs upon application of a suitable potential, then the polyyne material is deemed electrosensitive.

As is apparent from publications of such investigators as Arthur Seher, Ferdinand Bohlmann et al., R. -H. Jones and M. C. Whiting procedures are known in the art for preparation of polyacetylenic compositions. Preparatory techniques are also taught in US. Pats. 2,816,149; 2,941,- 014; 3,065,283; etc. General preparative methods include: oxidative coupling or oxidative dehydrocondensation reactions of numerous terminal acetylenic compounds to prepare as desired, symmetrical and unsymmetrical polyyne compounds; dehydrohalogenation reactions to provide compounds containing acetylenic bonds; and variations, modifications and combinations of such two basic reactions to provide preparative routes for a multitude of electrosensitive polyacetylenic compositions of matter.

Illustrative and representative of the sensitive crystalline polyacetylenic compounds to which the invention is applicable are those disclosed in US. Pats. 3,501,297; 3,501,- 302; 3,501,303; and 3,501,308. Additional useful materials are those polyacetylenic compounds disclosed in the copending applications of James C. Fleming and Paul E. Driedger, entitled Photosensitive Elements Comprising Polyacetylenic Bis-Urethanes, Ser. No. 153,060, now abandoned; Melvin S. Bloom and Sally S. Fico, entitled Photosensitive Elements Comprising Polyacetylenic Amine Salts, Ser. No. 153,059; and Melvin S. Bloom, entitled Photosensitive Elements Comprising Alkylamide Polyacetylenic Compounds, Ser. No. 153,053, now abandoned, all filed June 14, 1971. Typically, the polyyne crystals have a size in the range of about 0.1 to about 1.5 microns.

Some representative polyyne materials include:

No. Compound Docosadiynedioic acid, monomethyl ester Methyl-21-[N-( 2 hydroxyethyl)carbamoyl]-10,12-

heneicosadiyneoate Octa-3,5-diynylene-1,8-bis-n-butylcarbamate Hexylammonium 20 (N-hexylcarbamoyl)-9,1l-

eicosadiyne-l-carboxylate Deca-4,6-diynylene-1,10-bisphenylcarbamate 4,6-Decadiyne-1,10-dioldimesylate 2,4-Hexadiyne-1,6-diol-bis-p-tolylurethane 1,6-Bismorpholino-2,4-hexadiyne In accordance with this invention, the polyyne material can be in the form of a binder-free layer or can involve a binder material. Exemplary binder materials include: natural and synthetic plastics, resins, waxes, colloids, gels and the like, including gelatins (desirably photographicgrade gelatin), various polysaccharides including dextran, dextrin, hydrophilic cellulose ethers and esters, acetylated starches, natural and synthetic waxes including parafiin, beeswax, polyvinyllactams, polymers of acrylic and methacrylic esters and amides, hydrolyzed interpolymers of vinyl acetate and unsaturated addition polymerizable compounds such as maleic anhydride, acrylic and methacrylic esters and styrene, vinyl acetate polymers and copolymers and their derivatives including completely and partially hydrolyzed products thereof, polyvinyl acetate, polyvinyl alcohol, polyethylene oxide polymers, polyvinylpyrrolidine, polyvinyl acetals including polyvinyl acetaldehyde acetal, polyvinyl butyraldehyde acetal, polyvinyl sodiumo-sulfobenzaldehyde acetal, polyvinyl formaldehyde acetal, and numerous other known photographic binder materials. As is well known in the art in the preparation of smooth uniform continuous coatings of binder materials, there may be employed therewith small amounts of conventional coating aids as viscosity controlling agents, leveling agents, dispersing agents, and the like.

An especially useful technique for forming layers of polyyne material in a binder is described in Fico and Manthey application Ser. No. 153,061, filed June 14, 1971, and entitled Stable Photosensitive Polyacetylenic Elements and the Preparation Thereof, now abandoned. Of course, various other methods well known in the art can be used such as described in Foltz US. Pat. No. 3,501,302, issued Mar. 17, 1970.

If it is desired to prepare a binder-free layer of polyyne material, this can be accomplished by applying to a substrate a solution of polyyne in a suitable solvent followed by drying.

Suitable supporting materials for the electrosensitive layers of the present invention can include any of a wide variety of electrically conducting supports, for example, various conducting papers; aluminum coated paper; aluminum-paper laminates; metal foils such as aluminum foil, zinc foil, etc.; metal plates such as aluminum, copper, zinc, brass, and galvanized plates; vapor deposited metal layers such as silver, nickel or aluminum on conventional glass or film supports such as cellulose acetate, poly(ethylene terephthalate), polystyrene and the like conducting supports. Another useful conducting support can be prepared by coating a support material such as poly(ethylene terephthalate) with a layer containing a semiconductor dispersed in a resin as described in US. Pat. 3,245,833 or vacuum deposited on the support. Additionally, a suitable conducting coating can be prepared from the sodium salt of a carboxyester lactone of a maleic anhydride-vinyl acetate copolymer. Such kinds of conducting layers and methods for their optimum preparation and use are disclosed in US. 3,007,901; 3,245,833 and 3,267,807.

In accordance with this invention, the polyyne layer is subjected to a concentrated electrical potential between a small electrode or a plurality of such electrodes and a conductive backing member. As discussed previously, the electrical connection can be made directly to the conductrve portion of the support or a conductive plate can simply be pressed into contact with the conductive support of the element if the support is conductive throughout. A small pin electrode can be used which is stationary and closely spaced to the electrosensitive layer. The electrode can be so closely spaced as to actually touch the layer. Typically, this electrode is spaced about 0.005 to about 10.0 mm. away from the sensitive layer. With a stationary electrode, the sensitive element would typically be moved relative thereto. Other embodiments would involve a stationary element with a moving electrode. If desired, both the electrode and the element could be moved relative to one another during application of the imaging electrical potential. Still other embodiments involve a stationary element with an associated stationary array of small electrodes as seen, for example, in a Printapix tube. The applied potential need only be sufficient to image the polyyne material. Typical useful potentials are of the order of about to about 1500 volts DC. or unidirectional A.C. These values, of course, are dependent upon the particular electroseusitive materials and configuration used. It is believed that image formation results from the ionization of the ambient atmosphere in the region of the electrode. The resultant ionized species then initiate polymerization of the polyyne material.

The procedures of this invention are useful for a variety of applications. For example, the present system can be used for recording oscillographic information. The pin electrode could be substituted for the fountain pen of an x-y recorder and used to plot curves. Various analog data can be recorded with the present system. As mentioned previously, the elements described herein can also be used in connection with a Printapix tube to record information therefrom.

The elements useful herein can have a thin protective layer over the electrosensitive layer. For example, a thin layer of gelatin or polyvinyl alcohol can be used to impart scratch and abrasion resistance to the element. As previously discussed, the photosensitivity of the polyyne material is not important. However, if the layer is quite photosensitive, it is desirable to render the element nonphotosensitive in some manner so as to avoid premature imaging as a result of a photoexposure. This can be accomplished by the incorporation of an ultraviolet absorbing material in the polyyne layer or as a separate overcoat. Most photosensitive polyynes have their greatest sensitivity in the ultraviolet region of the spectrum. However, if the polyyne is more sensitive in the visible region of the spectrum, then some type of visible-light absorbing filter layer, etc., would be desirable.

The following examples are included for a further understanding of the invention.

EXAMPLE 1 A solution is prepared comprising 10,12-docosadiynedioic acid, monomethyl ester (Compound 1) 1.0 Dichloromethane 25.0

The solution is filtered using a fine fritted glass funnel and coated on Weyerhaeuser Conducting Base G (a conducting paper manufactured by the Weyerhaeuser Co.) using a .004 inch coating knife. A sample of this polyyne coated paper is placed in contact with a grounded metal plate (conducting side down). A high frequency vacuum tester (Tesla coil) is passed over the polyyne surface so that the spark is at a distance of approximately mm., tracing out the letters RWS. A blue image of the tracing on a white background is instantaneously produced.

EXAMPLE 2 A solution is prepared containing 5% by weight of the polyyne of Example 1 in dichloroethane. The solution is filtered and applied to a .004 thick poly(ethylene terephthalate) support upon which a film of metallic nickel having an optical density of 0.15 has been evaporated. The coating solution is applied over the nickel layer with a .004 inch coating knife and dried resulting in a colorless, translucent flm of microcrystalline polyyne with an estimated thickness of 4.0 ,um. FIG. 1 shows the basic configuration of the polyyne element and recording electrode configuration used in this example. The electrode assembly is mounted on a positioning device which allows the electrode to be moved in the plane of the film as well as perpendicular to the film so that the separation between the stainless steel electrode and the polyyne surface can be varied between approximately 0.125 mm. to 0.500 mm. A silver conducting paste connection is made with the nickel conducting layer and a potential is applied between this layer and the movable electrode. With applied voltages of the order of 400-1200 volts (of either polarity) a blue form of the polyyne is produced in the area directly beneath the electrode. Image density is somewhat dependent on the distance between the electrode 7 and the polyyne surface with the density increasing as this distance decreases. By moving the electrode in the plane of the film, an image can be printed using the techniques of the invention. The words PAUL and FRED are produced in this manner without requiring any additional treatment.

EXAMPLE 3 The solution of Example 2 is applied in a uniform, thin layer to a sheet of conductive paper by spraying the solution from a container pressurized with an inert propellant. The paper used has a reported bulk conductivity of 10- (ohm-cm.) The basic configuration of the polyyne element and the experimental configuration used are shown in FIG. 2. In this example, because of the bulk conductivity of the paper, electrical connection with the conducting substrate is made by simply pressing the paper firmly against the metal support plate and holding it in this position during exposure as in Example 1. The polyyne is converted to a blue form in areas directly beneath the electrode when the applied potential is in the range of about 600 to 1200 volts and the distance between the electrode and the polyyne surface is about .0125 mm. to 0.500 mm. An image is formed regardless of the polarity of the moving electrode. By moving the electrode in a plane parallel to the polyyne layer with the potential applied, the word PAUL is produced on the polyyne element without requiring any additional treatment.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

'We claim:

1. In a process of recording information on an electrosensitive element by applying an electrical potential between at least one electrode closely spaced to said element and a conducting backing member on a side of the element opposite said electrode, the improvement wherein said element is comprised of a conducting support having thereon a layer of an electrosensitive crystalline polyacetylenic compound having a minimum of two acetylenic linkages as a conjugated system.

2. The invention as described in claim 1 wherein said electrosensitive layer of polyacetylenic compound includes a polymeric, film-forming binder.

3. The invention as described in claim 1 wherein said conductive support is conductive paper.

4. The invention as described in claim 1 wherein said element contains an ultraviolet light filter means.

5. In a process of recording information on an electrosensitive element by applying an electrical potential between at least one electrode closely spaced to said element and a conducting backing member on a side of the element opposite said electrode, the improvement wherein said element is comprised of a conductive paper support having thereon a layer of an electrosensitive crystalline polyacetylenic compound having a minimum of two acetylenic linkages as a conjugated system, said crystalline compound having an average particle size of about 0.1 to about 1.5 microns.

References Cited UNITED STATES PATENTS 2,063,992 12/1936 Elsey 2042 2,606,807 8/1952 Pessel 204-2 2,653,126 9/1953 Greig 20 -2 2,683,111 7/ 1954 Greig 204-2 3,347,868 10/ 1967 Martin 204--2 GERALD L. KAPLAN, Primary Examiner T. TUFARIELLO, Assistant Examiner US. Cl. X.R. 117-201 

